3of3New slots for bicycles are seen on the newest Bart train during its inaugural ride Friday, Jan. 19, 2018 at MacArthur Station in Oakland, Calif.Photo: Jessica Christian, The Chronicle

Less than two weeks after making their debut, all 10 of BART’s new $2 million cars were back in the shop.

“They are undergoing maintenance,” was all BART spokesman Jim Allison would say when we asked him why the cars were pulled off-line Thursday morning.

Six of the cars were back in service by nighttime.

It was at least the second time in as many weeks that the cars, which were track-tested for months after being delivered by the Canadian firm Bombardier, were sent to the yard for repairs. The first sidelining came within days of their Jan. 19 debut, when one of the new cars had a problem and all 10 went in for a check.

BART spokeswoman Alicia Trost denied a report that the problem involved brakes, saying only that the cars were taken out for maintenance.

Allison said the latest sidelining was no big deal. “We don’t have any expectations that all 10 cars will be out carrying passengers each and every day,” he said. “The cars and personnel are in a break-in period.”

BART officials declined to say how long the break-in period would last.

When we asked for details on the latest repair job — such as what type of work was being done on the new cars and exactly how many had problems — Allison said, “You have our response.”

So we called Robert Raburn, president of the BART Board of Directors. The repairs were news to him, but after making a couple of calls, he said four of the 10 cars were being worked on. Among them was one of the two control cars, where the operator rides at the front of the train.

Raburn, however, said he didn’t know what the repair issue is.

A man holds onto one of the latest additions to BART’s newest train, a group of center poles, during its inaugural ride last month.

Photo: Jessica Christian, The Chronicle

Trost said it was “not unexpected” that some cars would need work. In fact, she indicated in an email, there have been other instances when the cars had to go out of service.

“It’s a different mix every day ... not the same cars out,” she wrote. “No major issues and no (defect) common to all cars.”

She added, “We had projected that about seven out of the 10 new cars would be available for passenger service on any given day for the initial period of passenger service.”

In other words, on any given day, almost a third of the new cars could be in the shop.

“With any new machine of considerable complexity, issues will occur that will require attention,” Trost said in the email. “Some of the cars are due for preventative maintenance (lubrication, changing filters, etc.) because they’ve already logged more than 75,000 miles of testing.”

Others, she said, are in the shop for “corrective repairs” or “engineering evaluation.”

BART has a $2.6 billion contract with Bombardier for about 150 new cars every year until the transit system’s old fleet is replaced. By 2022, BART expects to have a fleet of 775 cars, up from the current 669.

Whatever repairs are being made to the first of the new cars, they’ll be covered by a two-year warranty BART has with the Canadian firm.

Rebounding: Talk that the fight has gone out of embattled San Francisco Supervisor Jeff Sheehy looks to be premature.

Sheehy was appointed last year to his District Eight seat by the late Mayor Ed Lee. If he loses his June election battle against City College of San Francisco Trustee Rafael Mandelman, the balance of power at the Board of Supervisors could tip in progressives’ favor.

Mandelman has lined up an impressive list of supporters on the left, including mayoral candidate and former state Sen. Mark Leno, former Assemblyman Tom Ammiano, former Mayor Art Agnos and all five of the board’s sitting progressives.

Sheehy did little to help his cause with moderates when he joined the board’s progressives last month in voting to replace acting Mayor London Breed with Mark Farrell.

To make matters worse, Larry Tramutola — Sheehy’s second campaign consultant in three months — abruptly resigned days before the vote. He sent Sheehy a “termination notice” blasting him for his “unwillingness to do the work necessary to win” — including missing campaign meetings, not working the phones hard enough for contributions, and being a pain for campaign staffers to deal with.

When we asked Sheehy about the leaked memo, he replied, “Obviously, this is a legal thing and is in the hands of the lawyers, so I can’t say anything.”

He didn’t elaborate on what he meant by “a legal thing.”

Tramutola tells us the split was unfortunate. “While I deeply respect Jeff and who he is — and what he had done over the years for the community — our styles didn’t necessarily mesh,” he said.

Sheehy has hired a new campaign consultant, Ben Tevelin, who ran the late Ed Lee’s get-out-the-vote operation in the 2011 mayoral election. He has also brought in Sharon Johnson — a onetime aide to former state Sen. John Burton and former city Supervisor Harry Britt — to run his office.

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX-TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross

Whether writing about politics or personalities, Phil Matier has informed and entertained readers for more than two decades about the always fascinating Bay Area and beyond. The blend of scoops, insights and investigative reporting can be found every Sunday, Monday and Wednesday in the Chronicle.